Conventional electron emitting devices emit hot electrons by heating an element such as a tungsten filament in a vacuum, or emit cold electrons by applying an electric field to carbon nanotubes. Currently, an electron emitting device including a graphene emitter using very thin graphene as an electron emitting source is developed. The electron emitting device including the graphene emitter may be driven at a low voltage to obtain a high current, easily produced in a large array structure, and thus applied to a large display apparatus, a lighting apparatus, a high-resolution electron microscope, etc. In addition, if an anode electrode is made of tungsten, copper, molybdenum, or the like, the electron emitting device may be used as an electron emitting source of an X-ray generator.